Light can be controlled using standard lenses and mirrors. These passive methods can be made active via mechanical motion. For example, mirrors can be placed on motorized stages or piezo mounts to move the mirror to control either the direction of light propagation and/or the total optical path length of a system. By altering the total optical path length, the optical phase delay (OPD) of the light may be controlled.
However, mechanical control over light is undesirable for several reasons. First, it is difficult to make such mechanical devices compact. Second, the mechanical nature of such moving devices have limited lifetimes due to mechanical wear and failure issues. Third, mechanical devices are inherently vibration sensitive, which limits the type of environment in which they can be used. Finally, mechanical devices necessitate a level of design complexity including gears, bearings, and other mechanical components, which add cost, expense, and maintenance issues to such designs.
As an alternate to mechanical devices, one may utilize conventional thermally controlled waveguides for the dynamic control of light. In this waveguide technique, the temperature of the waveguide can be used to alter the index of refraction for light traveling through the waveguide. Typically such thermo-optic approaches provide for only limited changes in index of refraction (dn/dt≈1.5×10−5/° C.), which in turn necessitates large temperature changes (up to 500° C.). These devices are therefore typically power consumptive, which is prohibitive for many applications.
As recognized by the present inventors, what is needed is a thermo-optic waveguide for controlling light that permits active control of the propagation of light through the waveguide.
It is against this background that various embodiments of the present invention were developed.